The present invention is related generally to internal combustion engines and, more specifically, to rotary internal combustion engines.
Various types of internal combustion engines exist today. The most commonly used internal combustion engine for powering automobiles is the familiar internal combustion gasoline engine having a cylinder head in which pistons, carried on a crankshaft, are reciprocated by explosion of a gas-air mixture ignited by spark plugs. This type of internal combustion engine uses cam operated poppet valves, push rods, and a flywheel, all governed by means of a relatively complicated timing device. Lately, while such engines have enjoyed great commercial success, their limitations are becomming more apparent in the face of stricter air pollution laws and higher fuel economy demanded by the purchasing public. Oftentimes, air pollution emission standards and fuel economy are competing design criteria. In an effort to satisfy both requirements, this type of engine has become more complicated thus increasing production and maintenance costs.
Another type of internal combustion engine which has received widespread commercial acceptance is the diesel engine. This engine is generally used for driving heavier equipment such as railway engines, heavy trucks, and the like, but has lately gained some acceptance as an automobile engine because of its fuel economy. The diesel engine operates on diesel fuel and generates power in a crankshaft by means of reciprocating pistons. Poppet valves, cams, push rods, etc., are governed by means of timing devices. Unfortunately, the diesel engine suffers from many of the same limitations as the gasoline engine in addition to being difficult to start in cold weather.
Another type of internal combustion engine, known as a rotator type rotary engine, employs multiple rotors having simple rotary motion with an equal number of pistons attached to each rotor. Each rotor is attached to a mechanism which permits free-wheeling rotary motion and allows each set of pistons to travel in a common toroidal cylinder. Fuel intake, compression, combustion, and exhaust occur simultaneously at different angular positions of the toroidal chamber. The sequence of events between the pistons attached to the first rotor is repeated between the pistons attached to the second rotor. However, the control of the rotary motion of the rotors, and hence the pistons, has not been perfected with the result of inconsistent combustion ratios, the inability to control the rpms of the engine, and the overall inability to deliver power at a constant rate.
Another type of rotary engine which has enjoyed some commercial success is the Wankel rotary engine. This engine uses a three-cornered rotary element which is eccentrically mounted to a drive shaft for travelling in a toroidal chamber. The chamber has periphreal intake and exhaust ports and is divided by the rotary element into three smaller chambers, each of which being analogous to a cylinder in the standard gasoline engine. To increase the volume of each small chamber, segments of the rotor rim are recessed. During the combustion expansion phase, unburned gas tends to flow at high velocity away from the combustion zone with the result that part of the charge is unburned. This limits performance and increases air pollution. In addition, poor fuel consumption, together with a tendency of the seals between the rotary element and the toroidal chamber to prematurely wear, have detracted from the mass production of this engine on scales anywhere near those of the common internal combustion gasoline engine.
Yet another type of rotary engine, known as the Tschudi rotary engine, utilizes pistons which travel in a circular or an orbital path. Intake, compression, combustion and exhaust occur simultaneously at different angular positions of the toroidal chamber. Two rotors are employed with a set of two pistons affixed 180.degree. apart on each rotor. One rotor travels at a constant angular velocity while the movement of the other rotor is controlled by a complex crank and gear arrangement which enables the second set of pistons to accelerate and decelerate so that the volume of the combustion chamber between the pistons can be varied. However, shock loads associated with starting and stopping the rotors at high speed can create problems in everyday use. Also, there is no way to increase power output except by increasing the diameter of the toroidal chamber or adding a second toroidal chamber. Either of these two options increases the weight to power output ratio beyond acceptable limits and increases production costs.
Despite the problems associated with the various types of internal combustion rotary engines discussed above, research and development continues in an effort to further improve this type of invention. For example, in U.S. Pat. No. 3,227,090 to Bartolozzi, a rotary engine has a toroidal chamber, the floor of which is comprised of two rings as best seen in FIG. 3 of the Bartolozzi patent. The rings are capable of rotating in one direction. Each annular ring carries radially opposed pistons which are ultimately driven by the combustion of an air-fuel mixture. By alternately driving the pisons, the rings are also alternately driven. A mechanism is provided for transmitting the rotary motion of the rings to a central shaft.
In U.S. Pat. No. 4,344,841 to Barlow, a rotary engine having a pair of coaxial and independently rotatable shafts is shown. Each shaft carries a pair of pistons. Correct control of the shafts, and hence control of the pistons, is effected by connecting the inner and outer shafts to a causal mechanism unit, in part consisting of a cam and rhomboid mechanism. The rhomboid mechanism consists of four rollers connected by links to form a four-sided geometric figure. Two of the links are connected to the inner shaft while two of the links are connected to the outer shaft. The rhomboid mechanism is located within a cam, the surface of which is precisely described. By requiring the rhomboid mechanism to travel along the cam surface, the movement of the pistons can be controlled. This mechanism is also used to couple power generated by the engine to an output shaft.
U.S. Pat. No. 1,904,892 to Trube discloses a rotary engine having two pairs of diametrically opposed pistons, each carried by a disc. The discs, and hence the pistons, are connected to rollers which are constrained to move along a camming surface provided by a cam member. In this manner, the movement of the pistons can be controlled.
U.S. Pat. No. 2,736,328 to Mallenckrodt discloses a rotary engine utilizing a combustion chamber, the floor of which is comprised of two relatively rotatable annular ring members, as in the Bartolozzi patent, and a causal control mechanism having a cam surface for controlling the relative movement of the pistons as in the Barlow and Trube patents.
Another example of a rotary engine is U.S. Pat. No. 2,147,290 to Gardner. This patent discloses a rotary engine wherein a first set of pistons is secured to a hub which is substantially one-half the length of the pistons. A second set of pistons is secured to a second hub, which is again substantially one-half the length of the pistons. One-half of the first set of pistons overhangs the second hub, while one-half of the second set of piston overhangs the first hub. A control means, shown generally in FIG. 3 of the Gardner patent, is eliptically-shaped with the opposite end walls thereof being substantially semi-circular, while the side walls are parellel for a major portion of their length. This is another example of a control means used to control the motion of the pistons. A rectangular piston seal, which is comprised of overlapping elements, two of which are L-shaped, lies in a continuous groove in each of the pistons are best seen in FIG. 2 of the Gardner patent. Suitable springs are provided for urging the sealing blade elements into yielding engagement with the cylinder walls. In addition to the rectangular compression seals carried by the pistons, rings are preferably fitted into the circular grooves in the end plates to prevent the escape of combustion gases between the adjacent hub and the end plate.
Despite substantial work by numerous individuals, rotary engines still suffer from substantial problems which have prevented their mass production and widespread use. For example, although numerous mechanisms have been devised for transferring the power developed by the rotary engine to an output shaft, such power transfer mechanisms have typically been complex and unreliable. Additionally, the movement of the pistons within the chamber must be precisely controlled in power is to be continuously and smoothly generated. The replacement of worn piston seals is a major task in a rotary engine because the piston seals lie at the very heart of the engine. Replacement of these seals is thus a very complicated and expensive procedure which has contributed to the cool reception in the marketplace of various types of rotary engines. Additionally, lubrication of the pistons is complicated by the fact that the pistons are travelling in a circular orbit. Although lubrication must be provided in order to enable the pistons to move smoothly and eliminate unnecessary wear, the lubricant must be removed from the inside of that portion of the chamber in which combustion takes place. Otherwise unacceptable emissions occur. Such lubrication systems have tended to be complex, expensive and unreliable. Rotary engines have also, in general, required numerous moving parts which leads to higher production and maintenance costs.